Anodizing apparatus, utilizing a perforated negative electrode

ABSTRACT

This invention is to reduce the influence of a gas generated by an anodizing reaction. A silicon substrate ( 101 ) to be processed is horizontally held. A negative electrode ( 129 ) is arranged on the upper side of the silicon substrate ( 101 ), and a positive electrode ( 114 ) is brought into contact with the lower surface of the silicon substrate ( 101 ). The space between the negative electrode ( 129 ) and the silicon substrate ( 101 ) is filled with an HF solution ( 132 ). The negative electrode ( 129 ) has a number of degassing holes ( 130 ) to prevent a gas generated by the anodizing reaction from staying on the lower side of the negative electrode ( 129 ).

FIELD OF THE INVENTION

The present invention relates to an anodizing apparatus, an anodizingsystem, a substrate processing apparatus and method, and a substratemanufacturing method.

BACKGROUND OF THE INVENTION

Porous silicon was found by A. Uhlir and D. R. Turner who were studyingelectropolishing of single-crystal silicon biased to a positivepotential in an aqueous solution of hydrofluoric acid.

Later, to exploit excellent reactivity of porous silicon, application ofporous silicon to the element isolation process in manufacturing asilicon integrated circuit was examined, and a full isolation technology(FIFOS: Full Isolation by Porous Oxidized Silicon) using a poroussilicon oxide film was developed (K. Imai, Solid State Electron 24, 159,1981).

Recently, an applied technology to direct bonding has been developed inwhich a silicon epitaxial layer is grown on a porous silicon substrate,and the substrate is bonded to an amorphous substrate or single-crystalsilicon substrate via the oxide film (Japanese Patent Laid-Open No.5-21338).

As another application example, porous silicon has received a great dealof attention as a photoluminescence or electroluminescence material thatemits light by itself (Japanese Patent Laid-Open No. 6-338631).

A conventional anodizing apparatus for manufacturing a substrate havinga porous silicon layer will be described below.

FIG. 20 is a view showing the arrangement of a conventional anodizingapparatus (Japanese Patent Laid-Open No. 60-94737). In this anodizingapparatus, anodizing tanks 1902 a and 1902 b made of Teflon (tradenameof du Pont in the U.S.A) as a material with HF resistance are arrangedto sandwich a silicon substrate 1901 from both sides. The anodizingtanks 1902 a and 1902 b respectively have O-rings 1904 a and 1904 b forsealing at portions where the silicon substrate 1901 is held. Theanodizing tanks 1902 a and 1902 b have platinum electrodes 1903 a and1903 b, respectively. After the silicon substrate 1901 is sandwiched bythe two anodizing tanks 1902 a and 1902 b, the anodizing tanks 1902 aand 1902 b are filled with HF solutions 1905 a and 1905 b, respectively.In this state, a DC voltage is applied between the electrodes by settingthe platinum electrode 1903 a as a negative electrode and the platinumelectrode 1903 b as a positive electrode. The silicon substrate 1901 isanodized, and a porous silicon layer is formed on thenegative-electrode-side surface of the silicon substrate 1901.

In such conventional scheme of vertically holding a silicon substrateand anodizing it, a gas (e.g., hydrogen gas) generated by the anodizingreaction may stay on the surface of the silicon substrate for a longtime or rise along the surface of the silicon substrate. In this case,the track of gas remains on the surface of the porous layer formed onthe silicon substrate. This makes the porous layer nonuniform to resultin poor quality and a decrease in yield and productivity. Hence, ademand has arisen for introduction of a new scheme of preventing a gasgenerated by the anodizing reaction from adversely affecting anodizing.

To obtain high quality and productivity for substrates having a poroussilicon layer, it is important to reduce contamination of a siliconsubstrate during anodizing, and reduce contamination of a siliconsubstrate during a series of processes including anodizing andassociated processes (e.g., washing and drying).

To increase productivity of substrates having a porous silicon layer, itis also important to increase the speed of the series of processesincluding anodizing and associated processes.

Additionally, in consideration of the recent tendency of an increase indiameter of silicon substrates, it is also important to propose a schemecapable of easily coping with the increase in diameter.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovesituation, and has as its object to provide a new anodizing scheme.

More specifically, it is an object of the present invention to, e.g.,prevent any influence of a gas generated by an anodizing reaction.

It is another object of the present invention to, e.g., prevent anycontamination of a substrate to be processed.

It is still another object of the present invention to, e.g., increasethe speed of a series of processes including anodizing and associatedprocesses.

It is still another object of the present invention to, e.g., facilitateto cope with an increase in diameter.

According to the first aspect of the present invention, there isprovided an anodizing apparatus for anodizing a substrate, characterizedby comprising a holding portion for substantially horizontally holdingthe substrate to be processed, a negative electrode arranged above thesubstrate to oppose the substrate, a positive electrode arranged underthe substrate, and an anodizing tank for filling a space between thesubstrate and the negative electrode with an electrolyte, wherein thenegative electrode has a function of preventing a gas from staying on alower side.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the negative electrode preferably has adegassing hole for preventing the gas from staying on the lower side.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the positive electrode preferably supplies acurrent to the substrate to be processed while being in direct contactwith a lower surface of the substrate in anodizing.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, of the positive electrode, at least a portionwhich comes into contact with the substrate to be processed ispreferably formed from a semiconductor material.

Preferably, the anodizing apparatus according to the first aspect of thepresent invention further comprises, e.g., an electrode support portionsupporting the positive electrode, and the electrode support portion hasa mechanism for attaching/detaching the positive electrode.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the positive electrode preferably has a chuckmechanism for chucking the substrate to be processed.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the chuck mechanism preferably comprises avacuum chuck mechanism.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the holding portion preferably holds aperipheral portion of the lower surface of the substrate to beprocessed.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the holding portion preferably has a chuckportion for holding the substrate to be processed by chucking aperipheral portion of the lower surface of the substrate.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the anodizing tank preferably has an openingportion at a bottom portion and can be filled with a liquid when theholding portion holds the substrate to be processed.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the positive electrode preferably comes intocontact with the lower surface of the substrate to be processed, insidethe opening portion.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., an electrode elevatingmechanism for vertically moving the positive electrode.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a rotary driving mechanismfor rotating the substrate to be processed substantially in a horizontalplane to remove the liquid sticking to the substrate.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a rotary driving mechanismfor, after the substrate is released from the holding portion, rotatingthe positive electrode chucking the substrate substantially in ahorizontal plane to rotate the substrate.

Preferably, in the anodizing apparatus according to the first aspect ofthe present invention, for example, the anodizing tank has, at a bottomportion, an opening portion for bringing the positive electrode intocontact with the lower surface of the substrate to be processed, and theholding portion is arranged in an annular shape along the openingportion at the bottom portion of the anodizing tank and holds theperipheral portion of the lower surface of the substrate to beprocessed.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., an electrode elevatingmechanism for vertically moving the positive electrode, and a rotarydriving mechanism for, after the electrode elevating mechanism moves thesubstrate to be processed upward to a position where the substrate isnot in contact with the holding portion, rotating the positive electrodechucking the substrate substantially in a horizontal plane to rotate thesubstrate.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a substrate manipulationmechanism for receiving the substrate to be processed from a conveyorrobot and causing the holding portion to hold the substrate.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a substrate manipulationmechanism for receiving the substrate to be processed from a conveyorrobot, causing the holding portion to hold the substrate, andtransferring the processed substrate to the conveyor robot or anotherconveyor robot.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., an elevating mechanism forreceiving the substrate to be processed from a conveyor robot at anupper portion of the anodizing tank, moving the substrate downward, andcausing the holding portion to hold the substrate.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a substrate elevatingmechanism for receiving the substrate to be processed from a conveyorrobot at an upper portion of the anodizing tank, moving the substratedownward, causing the holding portion to hold the substrate, receivingthe processed substrate from the holding portion, moving the substrateupward, and transferring the substrate to the conveyor robot or anotherconveyor robot.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the elevating mechanism preferably has a supportportion for supporting the substrate to be processed from the lower sideand vertically moves the substrate placed on the support portion.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the support portion preferablyreceives/transfers the substrate to be processed from/to the conveyorrobot in a substantially horizontal state.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the support portion preferably has a structurecapable of receiving/transferring the substrate to be processed from/tothe conveyor robot supporting the substrate from the lower side.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a driving mechanism formoving the negative electrode.

In the anodizing apparatus according to the first aspect of the presentinvention, for example, the driving mechanism preferably removes thenegative electrode from the anodizing tank when the substrate to beprocessed is to be held by the holding portion, and makes the negativeelectrode oppose the substrate when the substrate is to be anodized.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a supply portion forsupplying the electrolyte into the anodizing tank.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a discharge portion fordischarging the electrolyte from the anodizing tank.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a circulation system forcirculating the electrolyte while supplying the electrolyte into theanodizing tank and simultaneously discharging the electrolyte from theanodizing tank.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a supply portion forsupplying a cleaning solution into the anodizing tank after thesubstrate is anodized.

The anodizing apparatus according to the first aspect of the presentinvention preferably further comprises, e.g., a discharge portion fordischarging the cleaning solution from the anodizing tank.

The anodizing apparatus according to the first aspect of the presentinvention can preferably be used as, e.g., an apparatus for filling theanodizing tank with the electrolyte to anodize the substrate and thenfilling the anodizing tank with the cleaning solution to wash thesubstrate.

The anodizing apparatus according to the first aspect of the presentinvention can preferably be used as, e.g., an apparatus for filling theanodizing tank with the electrolyte to anodize the substrate, fillingthe anodizing tank with the cleaning solution to wash the substrate, andthen drying the substrate.

According to the second aspect of the present invention, there isprovided an anodizing apparatus for anodizing a substrate, characterizedby comprising an anodizing tank, a negative electrode, a positiveelectrode, a first supply portion for supplying an electrolyte to aspace between the negative electrode and the substrate using theanodizing tank to anodize the substrate by applying a voltage betweenthe negative electrode and the positive electrode, and a second supplyportion for supplying a cleaning solution to the substrate using theanodizing tank to wash the anodized substrate.

The anodizing apparatus according to the second aspect of the presentinvention preferably further comprises, e.g., a rotary driving mechanismfor rotating the washed substrate in the anodizing tank to dry thesubstrate.

According to the third aspect of the present invention, there isprovided a processing apparatus for a substrate, characterized bycomprising a process tank and processing means for performing, for thesubstrate in the process tank, at least two consecutive processes ofanodizing, washing, and drying.

In the substrate processing apparatus according to the third aspect ofthe present invention, for example, the processing means preferablyprocesses the substrate while keeping the substrate in a substantiallyhorizontal state.

In the substrate processing apparatus according to the third aspect ofthe present invention, for example, the processing means preferablyprocesses the substrate while supporting the substrate.only from a lowerside.

The substrate processing apparatus according to the third aspect of thepresent invention preferably further comprises, e.g., substratemanipulation means for receiving the substrate from a conveyor robot ina substantially horizontal state and processing the substrate, andtransferring the processed substrate to the conveyor robot in thesubstantially horizontal state.

In the substrate processing apparatus according to the third aspect ofthe present invention, for example, the substrate manipulation meanspreferably manipulates the substrate by supporting the substrate onlyfrom the lower side.

According to the fourth aspect of the present invention, there isprovided an anodizing system characterized by comprising any one of theabove anodizing apparatuses, a conveyor robot for transferring anunprocessed substrate to the anodizing apparatus, receiving theprocessed substrate from the anodizing apparatus, and conveying theprocessed substrate to a predetermined position, and a control sectionfor controlling anodizing by the anodizing apparatus and substrateconveyance by the conveyor robot.

According to the fifth aspect of the present invention, there isprovided an anodizing system characterized by comprising any one of theabove anodizing apparatuses, a conveyor robot for transferring anunprocessed substrate to the anodizing apparatus while supporting thesubstrate from a lower side in a substantially horizontal state,receiving the anodized substrate from the anodizing apparatus whilesupporting the substrate from the lower side in the substantiallyhorizontal state, and conveying the anodized substrate to apredetermined position, and a control section for controlling anodizingby the anodizing apparatus and substrate conveyance by the conveyorrobot.

According to the sixth aspect of the present invention, there isprovided an anodizing system characterized by comprising any one of theabove anodizing apparatuses, a washing/drying apparatus for washing anddrying an anodized substrate, a conveyor robot for transferring anunprocessed substrate to the anodizing apparatus, receiving the anodizedsubstrate from the anodizing apparatus, transferring the anodizedsubstrate to the washing/drying apparatus, receiving the washed anddried substrate from the washing/drying apparatus, and conveying thewashed and dried substrate to a predetermined position, and a controlsection for controlling anodizing by the anodizing apparatus,washing/drying by the washing/drying apparatus, and substrate conveyanceby the conveyor robot.

According to the seventh aspect of the present invention, there isprovided a processing method for a substrate, characterized bycomprising the first step of substantially horizontally holding thesubstrate, making a negative electrode oppose an upper surface of thesubstrate, placing a positive electrode on a lower side of thesubstrate, and filling a space between the substrate and the negativeelectrode with an electrolyte, and the second step of applying a voltagebetween the negative electrode and the positive electrode to anodize thesubstrate while preventing a gas generated by an anodizing reaction fromstaying on a lower side of the negative electrode.

In the substrate processing method according to the seventh aspect ofthe present invention, for example, a negative electrode having astructure for preventing the gas from staying on the lower side ispreferably used as the negative electrode.

In the substrate processing method according to the seventh aspect ofthe present invention, for example, a negative electrode having adegassing hole for preventing the gas from staying on the lower side ispreferably used as the negative electrode.

According to the eighth aspect of the present invention, there isprovided a processing method for a substrate, characterized bycomprising the first step of anodizing the substrate using an anodizingtank, and the second step of washing the anodized substrate using theanodizing tank.

The substrate processing method according to the eighth aspect of thepresent invention preferably further comprises, e.g., the third step ofdrying the washed substrate in the anodizing tank.

According to the ninth aspect of the present invention, there isprovided a method of manufacturing a substrate, characterized bycomprising the steps of forming a porous layer on a surface of asubstrate by any one of the above substrate processing methods,preparing a first substrate having at least a semiconductor layer on theporous layer, bonding a second substrate to a surface of the firstsubstrate on a side of the semiconductor layer to prepare a bondedsubstrate stack, and separating the bonded substrate stack into twosubstrates at the porous layer.

Further objects, features and advantages of the present invention willbecome apparent from the following detailed description of theembodiments of the present invention with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E are views for explaining the steps in manufacturing anSOI substrate according to a preferred embodiment of the presentinvention;

FIG. 2 is a view showing the schematic arrangement of an anodizingapparatus according to the first embodiment of the present invention;

FIG. 3 is a view showing the schematic arrangement of the anodizingapparatus according to the first embodiment of the present invention;

FIG. 4 is a view showing the schematic arrangement of the anodizingapparatus according to the first embodiment of the present invention;

FIG. 5 is a view showing the schematic arrangement of the anodizingapparatus according to the first embodiment of the present invention;

FIG. 6 is a view showing the schematic arrangement of the anodizingapparatus according to the first embodiment of the present invention;

FIG. 7 is a view showing the schematic arrangement of the anodizingapparatus according to the first embodiment of the present invention;

FIG. 8 is a view showing the schematic arrangement of the anodizingapparatus according to the first embodiment of the present invention;

FIG. 9 is a view showing the schematic arrangement of the anodizingapparatus according to the first embodiment of the present invention;

FIG. 10 is a plan view showing part of the anodizing apparatus shown inFIGS. 2 to 9;

FIG. 11 is a plan view showing the schematic arrangement of an anodizingsystem having the anodizing apparatus shown in FIGS. 2 to 10;

FIG. 12 is a flow chart showing the schematic operation of the anodizingsystem 200 shown in FIG. 11;

FIG. 13 is a view showing the schematic arrangement of a post-processingapparatus according to the second embodiment of the present invention;

FIG. 14 is a view showing the schematic arrangement of thepost-processing apparatus according to the second embodiment of thepresent invention;

FIG. 15 is a view showing the schematic arrangement of thepost-processing apparatus according to the second embodiment of thepresent invention;

FIG. 16 is a view showing the schematic arrangement of thepost-processing apparatus according to the second embodiment of thepresent invention;

FIG. 17 is a plan view showing the schematic arrangement of an anodizingsystem according to the second embodiment of the present invention;

FIG. 18 is a view schematically showing the flow of processes of asilicon substrate by an anodizing system 500 shown in FIG. 17;

FIG. 19 is a flow chart schematically showing the operation of theanodizing system shown in FIG. 17 in processing one silicon substrate;and

FIG. 20 is a view showing the arrangement of a conventional anodizingapparatus (Japanese Patent Laid-Open No. 60-94737).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described below.

As a representative example of a substrate having a porous siliconlayer, which is manufactured by an anodizing apparatus according to apreferred embodiment of the present invention, a method of manufacturingan SOI substrate will be described first.

FIGS. 1A to 1E are views for explaining the steps in manufacturing anSOI substrate according to the preferred embodiment of the presentinvention.

In the step shown in FIG. 1A, a single-crystal Si substrate 11 isprepared, and a porous Si layer 12 is formed on the surface of thesingle-crystal Si substrate 11 using an anodizing apparatus according toan embodiment to be described later. As the porous Si layer 12, a porouslayer having a multilayered structure having a plurality of layers withdifferent porosities may be formed by changing the process conditionsstepwise.

In the step shown in FIG. 1B, a single-crystal Si layer 13 as anon-porous layer is formed on the porous Si layer 12 by epitaxialgrowth. The surface of the single-crystal Si layer 13 is oxidized toform an SiO₂ layer 14 as a non-porous insulating layer. With thisprocess, a first substrate 10 is formed.

In the step shown in FIG. 1C, a single-crystal Si substrate is preparedas a second substrate 20. The first substrate 10 and second substrate 20are brought into tight contact with each other at room temperature whilemaking the SiO₂ layer 14 of the first substrate 10 oppose the secondsubstrate 20. After that, these substrates may be subjected to anodicbonding, pressing, heating, or a combination thereof. With thisprocessing, a bonded substrate stack 30 in which the second substrate 20and SiO₂ layer 14 are firmly bonded is formed. The SiO₂ layer 14 may beformed either on the single-crystal Si substrate 11 side, on the secondsubstrate 20, or on both substrates as far as the state shown in FIG. 1Cis obtained upon bringing the first and second substrates into tightcontact with each other.

In the step shown in FIG. 1D, the bonded substrate stack 30 is separatedat the porous Si layer 12. The second substrate side (10″+20) has amultilayered structure of porous Si layer 12″/single-crystal Si layer13/insulating layer 14/single-crystal Si substrate 20. The firstsubstrate side (10′) has a structure wherein a porous Si layer 12′ isformed on the single-crystal Si substrate 11.

After the remaining porous Si layer 12′ is removed, and the surface onthe first substrate side (10′) after separation is planarized as needed,the first substrate is used as a single-crystal Si substrate 11 or asecond substrate 20 for forming a first substrate 10 again.

After the bonded substrate stack 30 is separated, in the step shown inFIG. 1E, the porous layer 12″ on the surface on the second substrateside (10″+20) is selectively removed. With this process, a substratehaving a multilayered structure of a single-crystal Si layer13/insulating layer 14/single-crystal Si substrate 20, i.e., an SOIstructure is obtained.

Formation of a porous silicon substrate by an anodizing reaction orformation of pores is performed in, e.g., an HF solution. It is knownthat the presence of holes in the silicon substrate is essential forthis process. The reaction mechanism is estimated as follows.

First, holes in a silicon substrate applied with an electric field in anHF solution are induced on the surface of the silicon substrate on thenegative electrode side. Consequently, the density of Si—H bondscompensating for the unbonded element on the surface of the siliconsubstrate becomes high. At this time, F ions in the HF solution on thenegative electrode side nucleophilically attack the Si—H bonds to formSi—F bonds. By this reaction, H₂ molecules are generated, andsimultaneously, one electron is emitted to the positive electrode side.

When Si—F bonds are formed, Si—Si bonds near the surface of the siliconsubstrate weaken due to the polarization characteristics of Si—F bonds.These weak Si—Si. bonds are attacked by HF or H₂O, and Si atoms on thecrystal surface form SiF₄ and are eliminated from the crystal surface.As a consequence, recessed portions are formed in the crystal surface. Afield distribution (field concentration) for preferentially attractingholes is generated at this portion. When this surface heterogeneityextends, etching of silicon atoms continuously progresses along theelectric field.

As described above, since the presence of holes is essential foranodizing, a p-type silicon substrate is preferable as a substrate to beprocessed. However, an n-type silicon substrate can also be used byirradiating it with light to prompt hole generation.

The solution used for anodizing is not limited to the HF solution, andany other electrolytic solution can be used.

Anodizing apparatuses according to preferred embodiments of the presentinvention will be described below.

[First Embodiment]

FIGS. 2 to 9 are views showing the schematic arrangement of an anodizingapparatus according to the first embodiment of the present invention.FIG. 10 is a plan view showing part of an anodizing apparatus 100 shownin FIGS. 2 to 9.

In the anodizing apparatus 100 according to the first embodiment of thepresent invention, a series of processes including anodizing, washing,and drying can be executed. According to this anodizing apparatus 100,the substrate need not be conveyed between units for individuallyperforming anodizing, washing, and drying. Hence, for example, 1) theproductivity is high, 2) the substrate can be prevented from dropping,and 3) the apparatus can be made compact.

In the anodizing apparatus 100, the series of processes includinganodizing, washing, and drying are performed while horizontally holdinga substrate to be processed. Hence, for example, when a substrate isreceived from a conveyor robot which horizontally holds and conveys thesubstrate, the substrate can be subjected to the series of processeswithout rotating the substrate (e.g., vertically setting the substrate).For this reason, the substrate manipulation efficiency can be improved.

In the anodizing apparatus 100, anodizing, washing, and drying areperformed while supporting a substrate to be processed from the lowerside. Hence, the risk of dropping the substrate can be reduced.

In the anodizing apparatus 100, a substrate is anodized whilesubstantially horizontally holding the substrate such that the surfaceon which a porous layer is to be formed is directed upward. With thisarrangement, a gas generated by an anodizing reaction can be quicklyremoved from the substrate surface, and the gas can be prevented frommoving along the substrate surface. According to this anodizingapparatus 100, a high-quality substrate can be manufactured at highyield. In the anodizing apparatus 100, a negative electrode opposing thesubstrate is arranged above the substrate because the substrate issubstantially horizontally held such that the surface on which a porouslayer is to be formed is directed upward. In this case, a gas (e.g.,hydrogen gas) generated by the anodizing reaction stays on the lowerside of the negative electrode, resulting in a decrease in anodizingefficiency. To prevent this, the anodizing apparatus 100 has a means forpreventing a gas from staying on the lower side of the negativeelectrode, thereby preventing any decrease in anodizing efficiency.

In the anodizing apparatus 100, since a substrate manipulation member isbrought into contact with only the lower surface of the substrate to beprocessed, i.e., the surface on which no porous layer is to be formed,contamination or damage to the substrate surface, i.e., the surface onwhich a porous layer is to be formed can be effectively prevented.

In the anodizing apparatus 100, since a current is supplied, via asilicon material, to the lower surface of the substrate to be processed,contamination of the lower surface of the substrate can be prevented.

In the anodizing apparatus 100, since a positive electrode is caused tochuck the substrate to be processed, satisfactory contact between thesubstrate and the positive electrode can be maintained, and failures inanodizing due to power supply errors can be reduced.

The arrangement of the anodizing apparatus 100 according to the firstembodiment of the present invention will be described below.

The anodizing apparatus 100 has an elevating mechanism for a siliconsubstrate 101 to be processed as a mechanism for receiving the siliconsubstrate 101 from a conveyor robot and moving the substrate to theprocess position and also transferring the processed silicon substrate101 to the conveyor robot or another conveyor robot. This elevatingmechanism vertically moves the silicon substrate 101 while supportingthe lower surface of the silicon substrate 101 from the lower side bythree lift pins 111 standing on an annular member 110. The annularmember 110 is coupled to the upper end of a rod 112 of an elevatingactuator (e.g., an air cylinder) 113 and driven by the actuator 113.

The anodizing apparatus 100 has an anodizing tank (process tank) 102 onthe upper side and a support member 131 for supporting the anodizingtank 102 on the lower side.

The anodizing tank 102 is made of a material having resistance to theprocess solution for anodizing. When an HF solution is employed as theprocess solution for anodizing, the anodizing tank 102 is preferablyformed from polytetrafluoroethylene (tradename: Teflon) as anHF-resistant material.

A circular opening portion 103 is formed at the bottom portion of theanodizing tank 102 so that a positive electrode 114 can be brought intodirect contact with the silicon substrate 101. An annular chuck pad 104is attached to the bottom portion of the anodizing tank 102 along theopening portion 103. The chuckpad 104 is formed from, e.g.,perfluoroethylene. The chuck pad 104 has on its surface an annulargroove 104 a for vacuum-chucking the silicon substrate 101. The groove104 a communicates with a vacuum line 134 through a suction hole 105.The vacuum line 134 is connected to a vacuum pump (not shown).

When the silicon substrate 101 is chucked by the chuck pad 104, theanodizing tank 102 can be filled with a process solution for anodizingor a process solution for washing.

The anodizing tank 102 has two injection ports 106 a and 106 b forinjecting process solutions into the tank and two discharge ports 108 aand 108 b for discharging process solutions. The injection ports 106 aand 106 b communicate with process solution supply lines 107 a and 107b, respectively. The discharge ports 108 a and 108 b communicate withprocess solution recovery lines 109 a and 109 b, respectively. Referringto FIGS. 2 to 9, only one set of injection port, discharge port, supplyline, and recovery line are shown for the illustrative convenience.

In this embodiment, to anodize the silicon substrate 101, a circulationsystem for circulating a process solution (e.g., an HF solution) foranodizing by supplying it into the anodizing tank 102 through the supplyline 107 a and recovering the process solution through the recovery line109 a is constructed. To wash the anodized silicon substrate 101, aprocess solution for washing (e.g., pure water) is supplied into theanodizing tank 102 through the supply line 107 b and recovered to arecovery tank through the recovery line 109 b. Each process solution maybe supplied from the upper side of the silicon substrate 101.

When the silicon substrate 101 is to be anodized, the anodizing tank 102is filled with a process solution for anodizing. In this state, anegative electrode 129 is dipped into the process solution and made tooppose the silicon substrate 101. Simultaneously, the positive electrode114 is brought into contact with the lower surface of the siliconsubstrate 101.

The negative electrode 129 has a plurality of degassing holes 130 toprevent a gas (e.g., hydrogen gas) generated by the anodizing reactionfrom staying on the lower side of the negative electrode 129. Instead offorming the degassing holes 130 in the negative electrode 129, amesh-like negative electrode 129 may be used.

The negative electrode 129 is coupled to the shaft of a motor 127through a coupling member 128 and manipulated by the motor 127. Morespecifically, when anodizing is to be performed, the negative electrode129 is pivoted by the motor 127 to an opposite position of the siliconsubstrate 101. In this state, the electrode surface of the negativeelectrode 129 is set horizontally. When a process other than anodizingis to be performed, the negative electrode 129 is pivoted by the motor127 to the upper side of the anodizing tank 102. The negative electrode129 is connected to the negative electrode of a power supply unit (notshown).

The motor 127 also has a function of finely adjusting the intervalbetween the negative electrode 129 and the silicon substrate 101 whilekeeping the negative electrode 129 and silicon substrate 101substantially parallel. This allows a change in anodizing condition.However, the negative electrode 129 can be vertically moved by only asmall amount while keeping the negative electrode 129 and siliconsubstrate 101 substantially parallel. To increase this amount, forexample, a manipulation mechanism for moving the negative electrode 129in the vertical direction is preferably employed.

The negative electrode 129 is preferably formed from a material havingresistance to a process solution for anodizing. For example, when an HFsolution is employed as the process solution for anodizing, the negativeelectrode 129 is preferably made of, e.g., platinum as an HF-resistantmaterial.

The positive electrode 114 is preferably formed from the same materialas that of the silicon substrate 101, i.e., a silicon material at atleast a portion in contact with the silicon substrate 101. This siliconmaterial preferably has a low resistivity. When the positive electrode114 is made of a silicon material, the silicon substrate 101 can beprevented from being contaminated by the material of the positiveelectrode 114. Since the positive electrode 114 does not come intocontact with the process solution (e.g., an HF solution) for anodizing,the surface of the positive electrode rarely changes its quality evenwhen the positive electrode 114 is formed from a silicon material.

The positive electrode 114 has on its surface an annular groove 115 forvacuum chuck to chuck the lower surface of the silicon substrate 101.The groove 115 communicates with a vacuum line 120 through a suctionhole 118 and sealing portion 119. The vacuum line 120 is connected to avacuum pump (not shown). The suction hole 118 communicates with the sidesurface of a rotating shaft 135 through a lower electrode 116 andelectrode support member 117. The annular sealing portion 119 isattached to the outer surface of the rotating shaft 135 to surround theoutlet of the suction hole 118. The sealing portion 119 is coupled tothe vacuum line 120. Hence, when the vacuum pump connected to the vacuumline 120 is actuated, the silicon substrate 101 can be chucked on thesurface of the positive electrode 114.

The lower electrode 116 is an electrode for applying a voltage at anequipotential to the entire surface of the positive electrode 114. Thelower electrode 116 preferably has a mechanism for attaching/detachingthe positive electrode 114 such that the positive electrode 114 can beeasily exchanged when it is contaminated or damaged.

The lower electrode 116 is connected to an annular electrode 121 fixedto the rotating shaft 135 through a lead line 122. The annular electrode121 is connected to a lead line 123 through a contact brush (not shown).The lead line 123 is connected to the positive terminal of a powersupply unit (not shown).

The lower electrode 116 is fixed on the electrode support member 117formed from an insulating material. The electrode support member 117 isfixed to the rotating shaft 135 of a motor 124. Hence, the positiveelectrode 114, lower electrode 116, electrode support member 117, androtating shaft 135 are integrally rotated by a driving force generatedby the motor 124.

The motor 124 is fixed on a rod 125 of an elevating actuator (e.g., anair cylinder) 126. The motor 124 and the structure thereon arevertically moved by a driving force generated by the elevating actuator126.

The support member 131 supports the anodizing tank 102 and also theelevating actuators 113 and 126.

FIG. 11 is a plan view showing the schematic arrangement of an anodizingsystem having the anodizing apparatus 100 shown in FIGS. 2 to 10.

An anodizing system 200 comprises two anodizing apparatuses 100 shown inFIGS. 2 to 10, a loader 201, an unloader 202, a conveyor robot 205, anda controller 210. In this anodizing system 200, the series of processesincluding anodizing, washing, and drying are executed parallelly usingthe two anodizing apparatuses 100, thereby improving the throughput.Three or more anodizing apparatuses may be used. This arrangementfurther improves the throughput.

FIG. 12 is a flow chart showing the schematic operation of the anodizingsystem 200 shown in FIG. 11. Processes shown in this flow chart arecontrolled by the controller 210. The controller 210 has an inputsection (operation section) for inputting various instructions, adisplay section for displaying the process situation and the like, amemory storing a program, a CPU for executing the program, and a drivingsection for driving each unit in accordance with an instruction from theCPU. The controller 210 can be constructed by a general computer system.

The anodizing system 200 starts processes shown in FIG. 12 when acarrier 203 which stores an unprocessed silicon substrate 101 is set onthe loader 201, a carrier 204 for storing a processed silicon substrate101 is set on the unloader 202, and the user instructs to startprocesses. For the descriptive convenience, only processes using oneanodizing apparatus 100 will be described below. In fact, this anodizingsystem 200 can simultaneously process two silicon substrates 101 usingtwo anodizing apparatuses 100.

First, in step S301, the elevating actuator 113 moves the lift pins 111upward, as shown in FIG. 2. The conveyor robot 205 extracts the siliconsubstrate 101 horizontally stored in the carrier 203 on the loader 201by supporting the lower surface of the substrate from the lower side,and places the silicon substrate 101 on the lift pins 111 while keepingthe substrate horizontal.

In step S302, as shown in FIG. 3, the elevating actuator 113 moves thelift pins 111 supporting the silicon substrate 101 from the lower sideto the lower end. In the course of downward movement of the lift pins111 to the lower end, the silicon substrate 101 is supported from thelower side by the chuck pad 104 at the bottom portion of the anodizingtank 102. Pressure in the groove 104 a of the chuck pad 104 is reducedto cause the chuck pad 104 to chuck the silicon substrate 101.

In step S303, as shown in FIG. 3, the negative electrode 129 is made tooppose the silicon substrate 101 by the motor 127.

In step S304, the elevating actuator 126 moves the positive electrode114 upward and brings the surface of the positive electrode 114 intocontact with the lower surface of the silicon substrate 101. Pressure inthe groove 115 on the surface of the positive electrode 114 is reducedto cause the positive electrode 114 to chuck the silicon substrate 101.

In step S305, as shown in FIG. 4, an HF solution 132 as a processsolution (electrolyte) for anodizing is injected into the anodizing tank102 from the injection port 106 a through the supply line 107 a to fillthe tank with the solution. At the same time, the HF solution iscirculated by a circulation system (not shown) while discharging the HFsolution 132 from the discharge port 108 a through the recovery line 109a.

This circulation system includes not only the anodizing tank 102,injection port 106 a, discharge port 108 a, supply line 107 a, andrecovery line 109 a but also a tank storing the HF solution 132,circulation pump, and filter. The circulation system may also include adensitometer and a concentration adjustment unit forincreasing/decreasing the concentration of the HF solution 132 inaccordance with the measurement result by the densitometer and thetarget concentration. The concentration of the HF solution 132 can bemeasured by, e.g., measuring the absorbance.

In step S306, as shown in FIG. 4, while circulating the HF solution 132,a voltage is applied between the negative electrode 129 and the positiveelectrode 114 by a power supply unit (not shown) to anodize the siliconsubstrate 101. With this process, a porous silicon layer is formed onthe surface of the silicon substrate 101. The power supply unit has afunction of adjusting the voltage and current to be output under thecontrol of the controller 210.

In step S307, as shown in FIG. 5, the negative electrode 129 isretreated upward by the motor 127.

In step S308, as shown in FIG. 5, supply of the HF solution is stopped,and the HF solution is recovered from the anodizing tank 102 through therecovery line 109 a.

In step S309, as shown in FIG. 6, the silicon substrate 101 is releasedfrom the chuck pad 104. The silicon substrate 101 is moved upward by theelevating actuator 126 and rotated at a high speed by the motor 124.With this operation, the HF solution sticking to the silicon substrate101 is removed by a centrifugal force. Next, as shown in FIG. 7, theelevating actuator 126 moves the silicon substrate 101 downward untilthe lower surface of the silicon substrate 101 comes into contact withthe chuck pad 104. After that, the chuck pad 104 is caused to chuck thesilicon substrate 101. Note that it is also effective to execute theseries of processes at a higher speed by omitting step S309.

In step S310, as shown in FIG. 7, a process solution (cleaning solution)133 for washing is injected into the anodizing tank 102 from theinjection port 106 b through the supply line 107 b to fill the tank. Atthe same time, the silicon substrate 101 is washed while recovering thecleaning solution 133 to a recovery tank from the discharge port 108 bthrough the recovery line 109 b.

As the cleaning solution 133, for example, pure water containing asurfactant is preferably used. More specifically, as the cleaningsolution 133, pure water containing about 5% to 10% of alcohol as asurfactant is preferably used. When a cleaning solution containing asurfactant is used, the cleaning solution can be caused to effectivelyenter a number of pores in the porous silicon layer formed on thesilicon substrate 101.

It is also effective to supply a surfactant to the silicon substrate 101in the first step and then supply pure water to the silicon substrate101 in the second step to wash the silicon substrate 101.

Alternatively, an ultrasonic cleaning method may be applied to executethis washing process while supplying an ultrasonic wave to the siliconsubstrate 101. When an ultrasonic wave is supplied, the washing time canbe shortened.

In step S311, as shown in FIG. 8, supply of the cleaning solution isstopped, and the cleaning solution is recovered from the anodizing tank102 into the recovery tank through the recovery line 109 b.

In step S312, as shown in FIG. 9, the silicon substrate 101 is releasedfrom the chuck pad 104. The silicon substrate 101 is moved upward by theelevating actuator 126 and rotated at a high speed by the motor 124.With this operation, the cleaning solution sticking to the siliconsubstrate 101 is removed by a centrifugal force so as to dry the siliconsubstrate 101.

In step S313, chuck of the silicon substrate 101 by the positiveelectrode 114 is canceled. At the same time, as shown in FIG. 2, theelevating actuator 113 moves the lift pins 111 upward to move thesilicon substrate 101 upward to a predetermined position while keepingthe silicon substrate 101 horizontally supported by the lift pins 111from the lower side. Next, the conveyor robot 205 receives the siliconsubstrate 101 on the lift pins 111 by supporting it from the lower sideand stores the silicon substrate in the carrier 204 on the unloader 202while keeping the horizontal state.

In step S314, it is determined whether an unprocessed silicon substrate101 remains. If YES in step S314, the flow returns to step S301 toexecute the processes in steps S301 to S313 for the silicon substrate101. If NO in step S314, the series of processes are ended.

[Second Embodiment]

An automatic anodizing apparatus according to the second embodiment ofthe present invention will be described below. The automatic anodizingapparatus of this embodiment has an anodizing apparatus 100 according tothe first embodiment as an apparatus for performing anodizing, and aseparate post-processing apparatus as an apparatus for executing washingand drying.

FIGS. 13 to 16 are views showing the schematic arrangement of thepost-processing apparatus according to the second embodiment of thepresent invention. FIG. 17 is a plan view showing the schematicarrangement of an anodizing system according to the second embodiment ofthe present invention.

The arrangement of a post-processing apparatus 400 according to thepreferred embodiment of the present invention will be described firstwith reference to FIGS. 13 to 16. This post-processing apparatus 400schematically has the same arrangement as the anodizing apparatus 100 ofthe first embodiment except that some functions are omitted. Morespecifically, since the post-processing apparatus 400 is used to washand dry an anodized silicon substrate, it has an arrangement obtained byomitting electrodes for anodizing and associated constituent elementsfrom the anodizing apparatus 100 according to the first embodiment. Notethat the anodizing apparatus 100 of the first embodiment can be directlyused as the post-processing apparatus.

In the post-processing apparatus 400, a negative electrode 129, and acoupling member 128 and motor 127 as associated constituent elements areomitted. In the post-processing apparatus 400, a lower electrode 116 anda lead line 122, annular electrode 121, and lead line 123 as associatedconstituent elements are also omitted.

The post-processing apparatus 400 has a chuck portion 144′ in place of apositive electrode 114. Like the positive electrode 114, the chuckportion 144′ is preferably formed from a silicon material. When thechuck portion 144′ is formed from a silicon material, a siliconsubstrate 101 can be prevented from being contaminated by the materialof the chuck portion 114′.

The post-processing apparatus 400 has a support portion 401 forsupporting the chuck portion 114′ in place of an electrode supportportion 117. The support portion 401 preferably has a mechanism forattaching/detaching the chuck portion 114′ such that the chuck portion114′ can be easily exchanged when it is contaminated or damaged.

The post-processing apparatus 400 has a rotating shaft 402 in place of arotating shaft 135. The rotating shafts 135 and 402 are different onlyin that the rotating shaft 135 has a structure for supplying power tothe silicon substrate 101 while the rotating shaft 402 does not have thestructure.

The post-processing apparatus 400 has, e.g., a process tank 102′ havingthe same structure as that of the anodizing tank of the anodizingapparatus 100 according to the first embodiment.

An anodizing system 500 according to the preferred embodiment of thepresent invention will be described next with reference to FIG. 17. Theanodizing system 500 comprises two anodizing apparatuses 100 a and 100 bshown in FIGS. 2 to 10, two post-processing apparatuses 400 a and 400 bshown in FIGS. 13 to 16, a loader 201, an unloader 202, a conveyor robot205, and a controller 510. In this automatic anodizing system 500,anodizing, washing, and drying are executed parallelly using the twoanodizing apparatuses and two post-processing apparatuses, therebyimproving the throughput. Three or more anodizing apparatuses andpost-processing apparatuses may be used. This arrangement furtherimproves the throughput.

FIG. 18 is a view schematically showing the flow of processes of asilicon substrate by the anodizing system 500 shown in FIG. 17.Referring to FIG. 18, substrate No. x (e.g., substrate No. 1) indicatesthe number of a silicon substrate to be processed. In addition, tx(e.g., t1) indicates an operation sequence of the conveyor robot 205,and the silicon substrate 101 is conveyed in the order of t1, t2, t3, .. . Horizontal lines in FIG. 18 indicate processes by the firstanodizing apparatus 100 a, second anodizing apparatus 100 b, firstpost-processing apparatus 400 a, and second post-processing apparatus400 b. Oblique lines in FIG. 18 indicate conveyance by the conveyorrobot 205.

In the anodizing system 500, anodizing and washing/drying are executedby different apparatuses. For this reason, a process solution foranodizing and process solution for washing (cleaning solution) can beprevented from mixing in the tank.

FIG. 19 is a flow chart schematically showing the operation of theanodizing system shown in FIG. 17 in processing one silicon substrate.

First, in step S601, an elevating actuator 113 of the anodizingapparatus 100 a or 100 b moves lift pins 111 upward, as shown in FIG. 2.The conveyor robot 205 extracts the silicon substrate 101 horizontallystored in the carrier 203 on the loader 201 by supporting the lowersurface of the substrate from the lower side, and places the siliconsubstrate 101 on the lift pins 111 of the anodizing apparatus 100 a or100 b while keeping the substrate 101 horizontal.

In step S602, as shown in FIG. 3, the elevating actuator 113 of theanodizing apparatus 100 a or 100 b moves the lift pins 111 supportingthe silicon substrate 101 from the lower side to the lower end. In thecourse of downward movement of the lift pins 111 to the lower end, thesilicon substrate 101 is supported from the lower side by a chuck pad104 at the bottom portion of an anodizing tank 102. Pressure in a groove104 a of the chuck pad 104 is reduced to cause the chuck pad 104 tochuck the silicon substrate 101.

In step S603, as shown in FIG. 3, a negative electrode 129 is made tooppose the silicon substrate 101 by a motor 127.

In step S604, an elevating actuator 126 of the anodizing apparatus 100 aor 100 b moves a positive electrode 114 upward and brings the surface ofthe positive electrode 114 into contact with the lower surface of thesilicon substrate 101. Pressure in a groove 115 on the surface of thepositive electrode 114 is reduced to cause the positive electrode 114 tochuck the silicon substrate 101.

In step S605, as shown in FIG. 4, an HF solution 132 as a processsolution (electrolyte) for anodizing is injected into the anodizing tank102 from an injection port 106 a through a supply line 107 a to fill thetank with the solution. At the same time, the HF solution 132 iscirculated by a circulation system (not shown) while removing the HFsolution 132 from a discharge port 108 a through a recovery line 109 a.

As described above, this circulation system includes not only theanodizing tank 102, injection port 106 a, discharge port 108 a, supplyline 107 a, and recovery line 109 a but also a tank storing the HFsolution 132, circulation pump, and filter. The circulation system mayalso include a densitometer and a concentration adjustment unit forincreasing/decreasing the concentration of the HF solution 132 inaccordance with the measurement result by the densitometer and thetarget concentration. The concentration of the HF solution 132 can bemeasured by, e.g., measuring the absorbance.

In step S606, as shown in FIG. 4, while circulating the HF solution 132,a voltage is applied between the negative electrode 129 and the positiveelectrode 114 by a power supply unit (not shown) to anodize the siliconsubstrate 101. With this process, a porous silicon layer is formed onthe surface of the silicon substrate 101. The power supply unit has afunction of adjusting the voltage and current to be output under thecontrol of the controller 510.

In step S607, as shown in FIG. 5, the negative electrode 129 isretreated upward by a motor 127.

In step S608, as shown in FIG. 5, supply of the HF solution is stopped,and the HF solution is recovered from the anodizing tank 102 through therecovery line 109 a.

In step S609, as shown in FIG. 6, the silicon substrate 101 is releasedfrom the chuck pad 104. The silicon substrate 101 is moved upward by theelevating actuator 126 and rotated at a high speed by the motor 124.With this operation, the HF solution sticking to the silicon substrate101 is removed by a centrifugal force.

In step S610, first, the silicon substrate 101 is released from thepositive electrode 114. Simultaneously, as shown in FIG. 2, theelevating actuator 113 moves the lift pins 111 upward to move thesilicon substrate 101 upward to a predetermined position while keepingthe silicon substrate 101 horizontally supported by the lift pins 111from the lower side.

Parallelly to this operation, in the post-processing apparatus 400 a or400 b, the elevating actuator 113 moves the lift pins 111 upward, asshown in FIG. 13.

The conveyor robot 205 receives the silicon substrate 101 on the liftpins 111 of the anodizing apparatus 10 a or 100 b by supporting thesubstrate from the lower side and places it on the lift pins 111 of thepost-processing apparatus 400 a or 400 b while keeping the siliconsubstrate 101 set horizontally.

In step S611, as shown in FIG. 14, the elevating actuator 126 of thepost-processing apparatus 400 moves the lift pins 111 to the lower endto bring the lower surface of the silicon substrate 101 into contactwith the chuck pad 104. After that, the chuck pad 104 is caused to chuckthe silicon substrate 101.

In step S612, as shown in FIG. 14, a process solution (cleaningsolution) 133 for washing is injected into the process tank 102′ of thepost-processing apparatus 400 a or 400 b from an injection port 106 bthrough a supply line 107 b to fill the tank. At the same time, thesilicon substrate 101 is washed while recovering the cleaning solution133 to a recovery tank from a discharge port 108 b through a recoveryline 109 b.

As the cleaning solution 133, for example, pure water containing asurfactant is preferably used. More specifically, as the cleaningsolution 133, pure water containing about 5% to 10% of alcohol as asurfactant is preferably used. When a cleaning solution containing asurfactant is used, the cleaning solution can be caused to effectivelyenter the porous silicon layer formed on the silicon substrate 101.

It is also effective to supply a surfactant to the silicon substrate 101in the first step and then supply pure water to the silicon substrate101 in the second step to wash the silicon substrate 101.

Alternatively, an ultrasonic cleaning method may be applied to executethis washing process while supplying an ultrasonic wave to the siliconsubstrate 101. When an ultrasonic wave is supplied, the washing time canbe shortened.

In step S613, as shown in FIG. 15, supply of the cleaning solution isstopped, and the cleaning solution is recovered from the process tank102′ of the post-processing apparatus 400 a or 400 b into the recoverytank through the recovery line 109 b.

In step S614, as shown in FIG. 16, the silicon substrate 101 is releasedfrom the chuck pad 104. The silicon substrate 101 is moved upward by theelevating actuator 126 and rotated at a high speed by the motor 124.With this operation, the cleaning solution sticking to the siliconsubstrate 101 is removed by a centrifugal force so as to dry the siliconsubstrate 101.

In step S615, the silicon substrate 101 is released from the positiveelectrode 114. At the same time, as shown in FIG. 13, the elevatingactuator 113 of the post-processing apparatus 400 a or 400 b moves thelift pins 111 upward to move the silicon substrate 101 upward to apredetermined position while keeping the silicon substrate 101horizontally supported by the lift pins 111 from the lower side. Next,the conveyor robot 205 receives the silicon substrate 101 on the liftpins 111 by supporting it from the lower side and stores the siliconsubstrate in the carrier 204 on the unloader 202 while keeping thehorizontal state.

According to the present invention, for example, the substrate to beprocessed is horizontally held, the negative electrode is arranged abovethe substrate, and a gas is prevented from staying on the lower side ofthe negative electrode, thereby reducing the influence of the gasgenerated by the anodizing reaction.

According to the present invention, for example, of the positiveelectrode, at least a portion that comes into contact with the substrateto be processed is formed from a semiconductor material, therebyreducing contamination of the substrate.

According to the present invention, for example the substrate to beprocessed is supported only from the lower side, thereby reducingcontamination of the substrate.

According to the present invention, for example, at least twoconsecutive processes of anodizing, washing, and drying are executed inone process tank, thereby increasing the speed of anodizing and a seriesof associated processes.

According to the present invention, for example, the substrate istransferred between the apparatuses while keeping it in the horizontalstate. This effectively prevents, e.g., drop of the substrate andfacilitates to cope with the increase in substrate diameter.

According to the present invention, for example, a series of processesare executed while supporting the substrate from the lower side in thehorizontal state. This effectively prevents, e.g., drop of the substrateand facilitates to cope with the increase in substrate diameter.

The present invention is not limited to the above embodiments andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore, to apprise the public of thescope of the present invention, the following claims are made.

What is claimed is:
 1. An anodizing apparatus for anodizing a siliconsubstrate, comprising: a holding portion for substantially horizontallyholding the substrate; a perforated negative electrode arranged abovethe substrate to oppose the substrate; a positive electrode arrangedunder the substrate; and an anodizing tank for filling a space betweenthe substrate and said negative electrode with an electrolyte, whereinsaid perforated negative electrode is adapted to prevent a gas fromstaying on a lower side.
 2. The apparatus according to claim 1, whereinsaid negative electrode has a degassing hole for preventing the gas fromstaying on the lower side.
 3. The apparatus according to claim 1,wherein said positive electrode supplies a current to the substrate tobe processed while being in direct contact with a lower surface of thesubstrate in anodizing.
 4. The apparatus according to claim 1, whereinof said positive electrode, at least a portion which comes into contactwith the substrate to be processed is formed from a semiconductormaterial.
 5. The apparatus according to claim 1, further comprising anelectrode support portion supporting said positive electrode, saidelectrode support portion having a mechanism for attaching/detachingsaid positive electrode.
 6. The apparatus according to claim 1, whereinsaid positive electrode has a chuck mechanism for chucking the substrateto be processed.
 7. The apparatus according to claim 6, wherein saidchuck mechanism comprises a vacuum chuck mechanism.
 8. The apparatusaccording to claim 1, wherein said holding portion holds a peripheralportion of the lower surface of the substrate to be processed.
 9. Theapparatus according to claim 1, wherein said holding portion has a chuckportion for holding the substrate to be processed by chucking aperipheral portion of the lower surface of the substrate.
 10. Theapparatus according to claim 1, wherein said anodizing tank has anopening portion at a bottom portion and can be filled with a liquid whensaid holding portion holds the substrate to be processed.
 11. Theapparatus according to claim 10, wherein said positive electrode comesinto contact with the lower surface of the substrate to be processed,inside the opening portion.
 12. The apparatus according to claim 1,further comprising an electrode elevating mechanism for verticallymoving said positive electrode.
 13. The apparatus according to claim 1,further comprising a rotary driving mechanism for rotating the substrateto be processed substantially in a horizontal plane to remove the liquidsticking to the substrate.
 14. The apparatus according to claim 6,further comprising a rotary driving mechanism for, after the substrateis released from said holding portion, rotating said positive electrodechucking the substrate substantially in a horizontal plane to rotate thesubstrate.
 15. The apparatus according to claim 1, wherein saidanodizing tank has, at a bottom portion, an opening portion for bringingsaid positive electrode into contact with the lower surface of thesubstrate to be processed, and said holding portion is arranged in anannular shape along the opening portion at the bottom portion of saidanodizing tank and holds the peripheral portion of the lower surface ofthe substrate to be processed.
 16. The apparatus according to claim 15,further comprising an electrode elevating mechanism for verticallymoving said positive electrode, and a rotary driving mechanism for,after said electrode elevating mechanism moves the substrate to beprocessed upward to a position where the substrate is not in contactwith said holding portion, rotating said positive electrode chucking thesubstrate substantially in a horizontal plane to rotate the substrate.17. The apparatus according to claim 1, further comprising a substratemanipulation mechanism for receiving the substrate to be processed froma conveyor robot and causing said holding portion to hold the substrate.18. The apparatus according to claim 1, further comprising a substratemanipulation mechanism for receiving the substrate to be processed froma conveyor robot, causing said holding portion to hold the substrate,and transferring the processed substrate to said conveyor robot oranother conveyor robot.
 19. The apparatus according to claim 1, furthercomprising an elevating mechanism for receiving the substrate to beprocessed from a conveyor robot at an upper portion of said anodizingtank, moving the substrate downward, and causing said holding portion tohold the substrate.
 20. The apparatus according to claim 1, furthercomprising a substrate elevating mechanism for receiving the substrateto be processed from a conveyor robot at an upper portion of saidanodizing tank, moving the substrate downward, causing said holdingportion to hold the substrate, receiving the processed substrate fromsaid holding portion, moving the substrate upward, and transferring thesubstrate to said conveyor robot or another conveyor robot.
 21. Theapparatus according to claim 20, wherein said elevating mechanism has asupport portion for supporting the substrate to be processed from thelower side and vertically moves the substrate placed on said supportportion.
 22. The apparatus according to claim 21, wherein said supportportion receives/transfers the substrate to be processed from/to saidconveyor robot in a substantially horizontal state.
 23. The apparatusaccording to claim 21, wherein said support portion has a structurecapable of receiving/transferring the substrate to be processed from/tosaid conveyor robot supporting the substrate from the lower side. 24.The apparatus according to claim 1, further comprising a drivingmechanism for moving said negative electrode.
 25. The apparatusaccording to claim 24, wherein said driving mechanism removes saidnegative electrode from said anodizing tank when the substrate to beprocessed is to be held by said holding portion, and makes said negativeelectrode oppose the substrate when the substrate is to be anodized. 26.The apparatus according to claim 1, further comprising a supply portionfor supplying the electrolyte into said anodizing tank.
 27. Theapparatus according to claim 1, further comprising a discharge portionfor discharging the electrolyte from said anodizing tank.
 28. Theapparatus according to claim 1, further comprising a circulation systemfor circulating the electrolyte while supplying the electrolyte intosaid anodizing tank and simultaneously discharging the electrolyte fromsaid anodizing tank.
 29. The apparatus according to claim 26, furthercomprising a supply portion for supplying a cleaning solution into saidanodizing tank after the substrate is anodized.
 30. The apparatusaccording to claim 29, further comprising a discharge portion fordischarging the cleaning solution from said anodizing tank.
 31. Theapparatus according to claim 1, wherein said apparatus can be used as anapparatus for filling said anodizing tank with the electrolyte toanodize the substrate and then filling said anodizing tank with thecleaning solution to wash the substrate.
 32. The apparatus according toclaim 1, wherein said apparatus can be used as an apparatus for fillingsaid anodizing tank with the electrolyte to anodize the substrate,filling said anodizing tank with the cleaning solution to wash thesubstrate, and then drying the substrate.
 33. An anodizing systemcomprising: an anodizing apparatus for anodizing a silicon substrate; aconveyor robot for transferring an unprocessed silicon substrate to saidanodizing apparatus, receiving the processed silicon substrate from saidanodizing apparatus, and conveying the processed silicon substrate to apredetermined position; and a control section for controlling anodizingby said anodizing apparatus and substrate conveyance by said conveyorrobot; wherein said anodizing apparatus including: a holding portion forsubstantially horizontally holding a silicon substrate to be anodized; aperforated negative electrode arranged above the silicon substrate tooppose the substrate; a positive electrode arranged under the siliconsubstrate; and an anodizing tank for filling a space between the siliconsubstrate and said negative electrode with an electrolyte, wherein saidperforated negative electrode is adapted to prevent a gas from stayingon a lower side.
 34. An anodizing system comprising: an anodizingapparatus for anodizing a silicon substrate; a conveyor robot fortransferring an unprocessed silicon substrate to said anodizingapparatus while supporting the unprocessed silicon substrate from alower side in substantially horizontal state, receiving the anodizedsilicon substrate from said anodizing apparatus while supporting theanodized silicon substrate from the lower side in the substantiallyhorizontal state, and conveying the anodized silicon substrate to apredetermined position; and a control section for controlling anodizingby said anodizing apparatus and substrate conveyance by said conveyorrobot; wherein said anodizing apparatus including: a holding portion forsubstantially horizontally holding a silicon substrate to be anodized; aperforated negative electrode arranged above the silicon substrate tooppose the substrate; a positive electrode arranged under the siliconsubstrate; and an anodizing tank for filling a space between the siliconsubstrate and said negative electrode with an electrolyte, wherein saidperforated negative electrode is adapted to prevent a gas from stayingon a lower side.
 35. An anodizing system comprising: an anodizingapparatus for anodizing a silicon substrate; a washing/drying apparatusfor washing and drying an anodized silicon substrate anodized by saidanodizing apparatus; a conveyor robot for transferring an unprocessedsilicon substrate to said anodizing apparatus, receiving the anodizedsilicon substrate from said anodizing apparatus, transferring theanodized silicon substrate to said washing/drying apparatus, receivingthe washed and dried silicon substrate from said washing/dryingapparatus, and conveying the washed and dried silicon substrate to apredetermined position; and a control section for controlling anodizingby said anodizing apparatus, washing/drying by said washing/dryingapparatus, and substrate conveyance by said conveyor robot; wherein saidanodizing apparatus including: a holding portion for substantiallyhorizontally holding a silicon substrate to be anodized; a perforatednegative electrode arranged above the silicon substrate to oppose thesubstrate; a positive electrode arranged under the silicon substrate;and an anodizing tank for filling a space between the silicon substrateand said negative electrode with an electrolyte, wherein said perforatednegative electrode is adapted to prevent a gas from staying on a lowerside.